The art of ink jet printing is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines have been implemented with ink jet technology for producing printed media. The contributions of Hewlett-Packard Company to ink jet technology are described, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985); Vol. 39, No. 5 (October 1988); Vol. 43, No. 4 (August 1992); Vol. 43, No. 6 (December 1992); and Vol. 45, No. 1 (February 1994).
Generally, an ink jet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an ink jet printhead. Typically, an ink jet printhead is supported on a movable print carriage that traverses over the surface of the print medium and is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
A typical Hewlett-Packard ink jet printhead includes an array of precisely formed nozzles in a nozzle plate that is attached to an ink barrier layer which in turn is attached to a thin film substructure that implements ink firing heater resistors and apparatus for enabling the resistors. The ink barrier layer defines ink channels including ink chambers disposed over associated ink firing resistors, and the nozzles in the nozzle plate are aligned with associated ink chambers. Ink drop generator regions are formed by the ink chambers and portions of the thin film substructure and the nozzle plate that are adjacent the ink chambers. The ink drop generators are commonly arranged in columnar arrays that are adjacent respective ink feed edges. For reasons such as timing logic and electrical interconnection, the ink drop generators of a given column are staggered relative to the adjacent ink feed edge, wherein ink chambers are at differing distances from the ink feed edge.
The thin film substructure is typically comprised of a substrate such as silicon on which are formed various thin film layers that form thin film ink firing resistors, apparatus for enabling the resistors, and also interconnections to bonding pads that are provided for external electrical connections to the printhead. The ink barrier layer is typically a polymer material that is laminated as a dry film to the thin film substructure, and is designed to be photodefinable and both UV and thermally curable. Ink is fed from one or more ink reservoirs to the various ink chambers around ink feed edges that can comprise sides of the thin film substructure or sides of ink feed slots formed in the substrate.
An example of the physical arrangement of the nozzle plate, ink barrier layer, and thin film substructure is illustrated at page 44 of the Hewlett-Packard Journal of February 1994, cited above. Further examples of ink jet printheads are set forth in commonly assigned U.S. Pat. Nos. 4,719,477 and 5,317,346.
Considerations with an ink jet printhead having staggered nozzles (heater resistors) include variation in ink drop size along an ink drop generator column which adversely affects print quality.
In an exemplary embodiment of the invention, a method for ejecting fluid from a device comprising: forming a plurality of fluid drop generators including: a plurality of heater elements located at different distances from a feed edge; a plurality of fluid chambers disposed over the plurality of heater elements, respectively, each fluid chamber defined by opposing walls that extend toward the feed edge; and a plurality of barrier islands each disposed between the opposing walls to define a pair of fluid channels; and selecting the size of the plurality of barrier islands to substantially equalize fluidic resistances in the plurality of fluid chambers.
In another exemplary embodiment, a method for ejecting fluid from a device comprising: forming a plurality of fluid drop generators located at different distances from a feed edge, the plurality of fluid drop generators having a plurality of fluid regions for receiving fluid and a plurality of barrier islands disposed within the fluid regions, respectively; and varying the volume of the plurality of fluid regions by varying the size of the plurality of barrier islands to thereby equalize fluidic pressure in the plurality of fluid regions.
In yet another exemplary embodiment, a fluid ejecting device comprising: a substrate having a feed edge and a plurality of heater elements located at different distances from the feed edge; a barrier layer having a plurality of fluid chambers disposed over the plurality of heater elements, respectively, the plurality of fluid chambers each defined by opposing walls that extend toward the feed edge; and a plurality of barrier islands disposed between the opposing walls, the size of the plurality of barrier islands is selected to substantially equalize the fluidic resistances within the plurality of fluid chambers.